Contract Manufacturing: Reliability

Complex Diagnostic Instruments

Improving the field reliability of complex instruments

24 January 2010

Improving the field reliability of complex diagnostic instruments and medical devices is a critical factor in reducing unscheduled service calls, extending the instrument's lifespan and increasing the overall profitability of the instrument.

The role of the contract manufacturer in improving the reliability of an instrument can extend well beyond simply building the device to a high standard. It can include proactively identifying areas for improvement, introducing procedures to collect and analyse feedback from the field, and providing spares that are compatible with all units in operation.

Proactive Management

Leading edge instruments by their nature contain a high quantity of custom, high tolerance parts. Reliability theory, such as that described in the worldwide standard MIL-HDBK-217, tells us that the more complex a device and the closer parts operate to their tolerance, the higher the probability that failures will occur.
Proactive management is a method utilised by the contract manufacturer to anticipate field issues, such as component drift or failures.

It is a highly disciplined approach to the collection and analysis of any data source that enables the contract manager to assist in the prevention of potential problems.

Best practices such as regular spares analysis, regular technical and logistical communications, and assistance with investigation of all field failures, ensure that any issues are detected as early as possible and that instrument reliability does not become a problem.

A contract manufacturer partner should:

  1. Help with the ongoing improvement of instrument alignments.
  2. Proactively identify potential failures through spares usage analysis.
  3. Use feedback on instrument critical components and in-process measurements to improve reliability.
  4. Deliver spares that are tested to work on any instruments in the field.
  5. Extend the lifespan and profitability of a complex instrument.

By monitoring spares usage, spikes in part demand can be detected which have not been reported as field failures. The consumption trends of parts from a central source, such as the contract manufacturer, can detect an issue of a global nature long before it is seen at the local, national or even multinational service level. For example a low cost part such as a computer hard drive may be changed in the field at regular service intervals due to corruptions, but may never be formally reported as a fault. In cases such as these early detection is essential if sufficient stock is to be maintained while corrective measures, such as a change of drive type or system software, are undertaken and validated.

The ability of a contract manufacturer to participate and provide highly relevant and valuable input into technical discussions on problems in the field, and in production, is critical for the continuous improvement in instrument reliability.

A contract manufacturer that also offers in-house design and engineering capability can potentially be even more effective in increasing reliability as they will be able to correct the reliability issues faster than manufacturers that need to liaise separately with the designer or the developer of the instrument.

Field Feedback

Complex electromechanical laboratory instruments are engineered to very tight tolerances because they are designed to operate with extremely small samples and highly accurate systems. Everything is measured on a micro scale; alignments are measured in micrometres, fluidics in microlitres, and detection in microvolts. It is therefore not surprising that many common field issues are due to instruments that fail to maintain these tight tolerances.

An example of a field issue is a mechanical alignment failure. This type of failure may not be obvious, but if regular control assays are being run there will be an increased number of the control test failures as the instrument drifts away from required tolerances.

The complication with mechanical alignment failures is that the instruments may still be within the original specification, but over time the company marketing the instruments may use them for more demanding assays, and these new assays require tighter tolerances.

A good contract manufacturing company will not be content to just deliver instruments within original specification, but will look for ways to improve the alignment, and aim to deliver machines in the middle of the tolerance band, not just meeting specification. This improved instrument alignment can be achieved through carefully executed and validated design changes, production monitoring and improved manufacturing processes.

By using regular field feedback on performance, the contract manufacturer can stay ahead of the accuracy requirements for future assays, and extend the lifespan of the current instrument before it requires a next generation upgrade.

Supply of Tested Spares

The longer an instrument remains in production, the larger the installed base of instruments. While all these units may still be within specification, they can all have different mechanical tolerances and alignments due to the ongoing refinement of the instrument over the years of production. This presents a challenge for the contract manufacturer to supply spares that not only work on the first unit delivered to the field, but also on the 100th or 1000th unit.

For example, a carbon muffler filter, which is fitted to a motor on a complex instrument to reduce noise and moisture, can have a wide variation of air flow characteristics depending on the batch supplied. Where batch variability of a spare part can impact performance of the instrument the contract manufacturer needs to test and assess each part before sending it out to the field. Therefore the contract manufacturer must have sophisticated processes to identify parts which are sensitive to varying levels of tolerance, and disciplined testing procedures to ensure that any part shipped to the field will work on any of the instruments in the field.

More than just Contract Manufacturing

A contract manufacturer can contribute significantly to the increased reliability of a complex instrument by proactively identifying reliability issues and monitoring field failures. The provision of tested spare parts, which are compatible with all field units, also significantly improves the reliability of instruments in the field. Where the contract manufacturer also possess in-house design and engineering expertise, the reliability improvements can be implemented even faster.